1. Field of the Invention
This invention relates to methods of sealing a conduit surrounding a utility line passing through a wall, one side of which is exposed to water, and the other side of which demarcates an area to be kept dry; and especially, the invention involves waterproofing electrical power line conduits entering underground vaults or basement walls.
2. Description of the Prior Art
Public utilities commonly run power lines underground through conduits which enter and leave underground vaults, typically of a concrete or masonry construction, that are accessed, for example, through ceiling towers to manholes, or by other service manways. Similarly, telephone lines, television cables and other public or private lines are run underground within the protective shield of a conduit for collection or distribution at underground vaults. The underground vault may be a power station and may contain switching and/or distribution junctions and/or transformers or other equipment which can be shortened or damaged by vault flooding, with potential loss of service to the customers of the utility and life endangering work situations for the utility company's workmen who enter the vault. A similar flooding problem is often presented in underground basement levels of building equipment rooms, where utility lines enter through conduits in the subterranean walls of the building.
In all these and other comparable situations in which an underground run of utility line shielded in a conduit is admitted into an underground vault, a source of water entrance into the vault is through the conduit itself. Water entry into an underground vault through underground conduit can be severe. For example, a power company's underground concrete vault measuring 10'.times.10'.times.20' and located in a coastal area in a Western state was consistently flooded with some 15,000 gallons of water within a 48 hour period from water entering the vault essentially through underground electrical power line conduits. Until the development and utilization of the hereinafter described invention to solve this problem of water entry to an underground vault, conventional efforts such as occluding the conduit inlet ports inside the vault walls with caulking materials or expanding plugs fitted around the power line had proven unsuccessful.
Another difficulty with electrical line conduits entering underground vaults is that power surges in the electrical lines cause line movement, and where several lines are carried by one conduit, the occurrence of water in the conduit can increase the risk of possible line to line power arcing and shorting, with consequent electrical failure.
Another method which applicant believes was unsuccessful was to use two oppositely disposed, spaced apart foam rubber flanges acting as dams which were to be fit around the electrical lines inside a conduit and along the axis of the conduit. Spacers were used between the flanges, with bolts, nuts and the spacers mounted on plates which abut the flat sides of the flanges. The nuts were tack welded to the most interior plates abutting the most interior flange. Accordingly, a cell was formed between the two dams, penetrated on opposite sides by the electrical lines and also the bolts running through the spacers. The cell was to be filled with oil or similar fluid and the dams compressed by use of the bolts. This structure is similar to that of FIG. 5 but with foam rubber dams. Applicant learned of this method and apparatus just prior to applicant's invention.